In recent years, artificial hair for direct implantation into human skin has been developed. However, the presently available artificial hair for implantation is not completely satisfactory because the shape of the hair root in the artificial hair does not enable the hair to be fixed firmly in place.
One proposal for solving this problem is shown in British Pat. No. 2006018A, wherein an artificial hair made of a monofilament resin has a loop part at the end thereof, the hair root being formed by tying the loop part vertically. The disadvantage of this arrangement is that the loop part is easily untied if it is wound singly. If the loop part is wound doubly or more, the knot is enlarged greatly with respect to the diameter of the hair root. When this type of hair is implanted, great injury is caused to the skin, resulting in much of the implanted hair falling our just after implantation. It is generally necessary to pull off the planted hair if inflammation or suppuration occurs on the skin after the hair has been fixed in place. However, with the artificial hair having a loop at the end thereof, if subcataneous tissue has interpenetrated the loop part, the pulled hair is snapped off at the joint of the knot, leaving the hair root part in the skin tissue which may cause additional medical problems.
To eliminate the above disadvantages, the present inventor previously proposed, in U.S. Pat. No. 4,588,408, to provide artificial hair which can be pulled out without leaving the root part in the skin tissue. In this instance, intersecting parts of looped hair root were fusion bonded using high frequency spot welding. This gave a freely adjustable peeling strength to the intersecting parts of the hair root. Accordingly, if a planted artificial hair is pulled with a force greater than that of a specified value, the boding is peeled at the intersection, and the loop shaped hair root becomes a single line of monofilament which can be pulled off without being left n the skin.
However, since the aritifical hair is bonded at only one point of intersection at the joint of the loop shaped hair root part, considerably firm fusion bonding is necessary to obtain the critical peeling strength at the intersection, in order to bear the pulling force. If this is the case, the fusion-bonded part becomes too thin, making it more likely that the monofilament will be snapped at the thinned part. Therefore, the conditions for fusion bonding, such as the welding force of a high frequency spot welding device, welding time, frequency of welds, etc., should be controlled carefully. Therefore, the percentage of defective products may increase considerably.